i feel it strange how people keep showing their age but do not show their date of birth. i think you shouldnt hide your date of birth its really odd. WHAT DO YOU SAY ABOUT IT?
Internet paranoia. Giving your age doesn't tell nearly as much as giving your exact birth date. People can find a lot of things out about you from your birth date if they really wanted to. With just an age, a much more vague number, there isn't much they can do.
If people choose to use their Date of Birth, it IS on their profile, in the upper right corner under "Mini Statistics" If they don't, that's their choice, it could be they don't want people knowing when their birthday is.
